In present medical practice, insertion of catheters into blood vessels and other body structures is most often accomplished by the percutaneous technique. The Percutaneous Technique is a term of art for a transcutaneous method that avoids surgical cut-down and dissection. Instead, a hollow-bore needle is employed to penetrate the skin or surface, traverse the subcutaneous tissue and other intervening structures, and enter the lumen of the blood vessel or body structure. Then a tracer or flexible filament, typically in the form of a metallic guidewire, is inserted through the bore of the needle so that it enters the vascular lumen and extends into the lumen to a distance sufficient to prevent accidental or inadvertent dislodgement. The flexibility of the guidewire reduces the likelihood of injury to the interior surface of the blood vessel within which it is advanced and manipulated to ensure a secure position. After the guidewire has been inserted into the vascular lumen, the practitioner, holding the proximal segment of the guidewire, i.e. the segment residing outside of the human body and above the skin, carefully withdraws the needle. Once the needle is entirely outside the body, it is slidably withdrawn from the guidewire and set aside. The guidewire now constitutes a smooth rail for slideable insertion of other devices, such as catheters of various types. This concept and method was innovated by Ivan Seldinger in 1953 and is often referred to as the “Seldinger technique”.
Building upon the original Seldinger technique for percutaneous access, Drs. Donald Desilets and Richard Hoffman in 1965 innovated the combination of a dilating catheter and a separate, thin-walled tubular conduit, a sheath, carried thereon to gain access to the vascular lumen via the guidewire. As detailed below, a dilating catheter with a conically tapered tip is advanced over and along the guidewire and dilates the arteriotomy puncture created by the needle up to the selected diameter of the chosen catheter. The main body of the dilating catheter carries a thin-walled sheath into the blood vessel. Further advancement of this catheter-sheath combination introduces the sheath into the blood vessel to a secure indwelling position, whereupon the guidewire and the dilating catheter are removed, leaving the sheath in place to provide a clear cylindrical path from skin into the vascular lumen. In this manner, the sheath provides a smooth unobstructed passageway for the insertion of diagnostic and/or therapeutic catheters and devices into the vascular system.
This procedure is referred to as the “Desilets-Hoffman technique” and is also referred to as the “modified Seldinger technique” or “Seldinger-Desilets-Hoffman technique”, or simply “SDH technique” as will be referred to herein. This technique can be applied to access blood vessels as well as other anatomic structures.